Our aluminium glazed porch door opens _outwards_ into the front garden, and thinking ahead to local problems around here - we don't really want to do open it fully that way unless the caller's business as been identified.
The door has become a bit of a de-facto front door, but looking around at door chains, guards and hotel latches - most of these suit doors that open inwards.
For instance, simple though it looks, I don't think this will work.
Door Guard Chrome Plated